1. Field of the Invention
The present invention relates generally to radiation therapy devices, and more particularly, to a removable electron multileaf collimator for use in a radiation therapy device.
2. Description of the Related Art
Conventional radiation therapy typically involves directing a radiation beam at a tumor in a patient to deliver a predetermined dose of therapeutic radiation to the tumor according to an established treatment plan. This is typically accomplished using a radiation therapy device such as the device described in U.S. Pat. No. 5,668,847 issued Sep. 16, 1997 to Hernandez, the contents of which are incorporated herein for all purposes.
The radiotherapy treatment of tumors involves three-dimensional treatment volumes which typically include segments of normal, healthy tissue and organs. Healthy tissue and organs are often in the treatment path of the radiation beam. This complicates treatment, because the healthy tissue and organs must be taken into account when delivering a dose of radiation to the tumor. While there is a need to minimize damage to healthy tissue and organs, there is an equally important need to ensure that the tumor receives an adequately high dose of radiation. Cure rates for many tumors are a sensitive function of the dose they receive. Therefore, it is important to closely match the radiation beam""s shape and effects with the shape and volume of the tumor being treated.
Both primary photon and primary electron beams may be used in radiation therapy. Accordingly, many existing radiation therapy devices include the ability to generate and deliver both photon and electron beams. Currently, clinical practice requires substantial manual intervention to use conformal electron treatment. Conformal photon fields typically are shaped using one or more collimating devices positioned between the source and the treatment area. Many of these photon beam collimating devices may be positioned automatically to deliver a desired photon field shape to a treatment area on a patient. Little manual intervention is required to administer photon radiation therapy.
Primary electrons are currently used on approximately 30% of all patients who undergo radiation therapy. Electron fields delivered via radiation therapy devices are typically shaped using either an off-the-shelf electron applicator (either rectangular or circular in cross-section) or a custom cutout formed of Cerrobend(copyright). Both of these beam shaping methods have limitations. Off-the-shelf electron applicators often unnecessarily irradiate portions of healthy tissue, since they do not precisely conform to the target. Custom cutouts formed of Cerrobende are highly conformal, but are costly to make, store and require special quality assurance. The Cerrobend(copyright) material may also require special handling because of the potentially toxic metals involved. Each of these approaches to electron field shaping also suffer in that they can be inefficient to use. A radiation therapist delivering a prescribed treatment must repeatedly enter the treatment room during treatment to insert the proper cutout for each field in the therapy. This is not only inefficient, but it effectively precludes the delivery of treatments which require electron field modulation in both intensity and energy at a single gantry position.
Oncologists would like to have the ability to prescribe mixed beam treatments which include the application of modulated electron and photon fields. With the exception of a few highly specialized and expensive devices, existing radiation therapy devices are unable to effectively provide such mixed beam treatments. Although existing radiation therapy devices do have the ability to deliver both electron and photon beams, the devices are unable to provide mixed beam treatments without requiring the repeated replacement and manual intervention by a therapist during treatment. It would be desirable to provide a radiation therapy device which is able to support mixed beam treatments where both photon and electron beams may be used in a single course of treatment and where the electron beam may be modulated in both intensity and energy without intervention by a radiation therapist. It would also be desirable to provide a system and method that allows the electron collimator assembly to be readily installed and removed as desired.
To alleviate the problems inherent in the prior art, and to allow the efficient and effective delivery of photon, electron, and mixed beam radiation therapy, embodiments of the present invention provide a system and method for use of a removable electron collimator.
According to one embodiment of the present invention, a radiation therapy device is provided which includes a radiation source positioned to direct a beam along a beam path toward a treatment area. The system includes a treatment head containing a first collimator controllable to selectively collimate the beam, and a second collimator removably positioned between the first collimator and the treatment area and controllable to selectively collimate the beam. In one embodiment, the second collimator is removably mounted on an accessory tray of the radiation therapy device. According to one embodiment, the first collimator is used to collimate a photon beam generated by the source, while the second collimator is used to collimate an electron beam generated by the source.
According to one embodiment of the present invention, an electron collimator for use in collimating an electron beam in a radiation therapy device is provided, where the collimator includes drive electronics, removably mounted on an exterior of an accessory tray of the radiation therapy device. The electron collimator also includes a plurality of leaves positionable by the drive electronics to move across a path of the electron beam, the plurality of leaves removably mounted on the accessory tray of the radiation therapy device.
The present invention is not limited to the disclosed preferred embodiments, however, as those skilled in the art can readily adapt the teachings of the present invention to create other embodiments and applications.